STIFFENER TAB FOR A SPINDLE MOTOR BASE PLATE
An apparatus and method are provided for stiffening a base plate of a spindle motor to improve shock resistance and vibration response, and thereby increase reliability and performance of a disc drive memory system. A stiffener tab for stiffening a base plate is connected to the base plate, extends from the base plate, and is dimensioned to fit adjacent to a stator tooth. Stiffening of a base plate is especially useful in the case of stamped base plate designs that typically have uniform thickness, whereas cast base plate designs are formed with thicker sections. In an aspect, the present invention stiffens a motor cup portion of the base plate, and replaces stiffness lost by removal of material from the base plate to form holes for recessing a stator into the base plate. Axial and angular displacement of a spindle motor during shock events and vibration are decreased.
Disc drive memory systems store digital information that is recorded on concentric tracks on a magnetic disc medium. At least one disc is rotatably mounted on a spindle, and the information, which can be stored in the form of magnetic transitions within the discs, is accessed using read/write heads or transducers. A drive controller is typically used for controlling the disc drive system based on commands received from a host system. The drive controller controls the disc drive to store and retrieve information from the magnetic discs. The read/write heads are located on a pivoting arm that moves radially over the surface of the disc. The discs are rotated at high speeds during operation using an electric motor located inside a hub or below the discs. Magnets on the hub interact with a stator to cause rotation of the hub relative to the stator. One type of motor has a spindle mounted by means of a bearing system to a motor shaft disposed in the center of the hub. The bearings permit rotational movement between the shaft and the sleeve, while maintaining alignment of the spindle to the shaft.
Disc drive memory systems are being utilized in progressively more environments besides traditional stationary computing environments. Recently, these memory systems are incorporated into devices that are operated in mobile environments including digital cameras, digital video cameras, video game consoles and personal music players, in addition to portable computers. These mobile devices are frequently subjected to various magnitudes of mechanical shock as a result of handling. As such, performance and design needs have intensified including improved resistance to shock events including axial and angular shock resistance, vibration response, and improved robustness.
The read/write heads must be accurately aligned with the storage tracks on the disc to ensure the proper reading and writing of information. Moreover, a demand exists for increased storage capacity and smaller disc drives, which has led to the design of higher recording areal density such that the read/write heads are placed increasingly closer to the disc surface. Precise alignment of the heads with the storage tracks is needed to allow discs to be designed with greater track densities, thereby allowing smaller discs and/or increasing the storage capacity of the discs. Because rotational accuracy is critical, many disc drives presently utilize a spindle motor having a fluid dynamic bearing (FDB) situated between a shaft and sleeve to support a hub and the disc for rotation. In a hydrodynamic bearing, a lubricating fluid is provided between a fixed member bearing surface and a rotating member bearing surface of the disc drive. Hydrodynamic bearings, however, suffer from sensitivity to external loads or mechanical shock. In particular, the stiffness of the fluid dynamic bearing is critical so that the rotating load is accurately and stably supported on the spindle without wobble or tilt.
Traditional base plate designs in larger disc drives are typically cast from aluminum. However, in the field of spindle motors for small form factor hard disc drives, thin stamped base plates are often employed for cost and manufacturing advantages. These stamped base plates are typically a steel material of generally uniform thickness, and therefore do not allow for localized thicker sections to optimize the tradeoff of stiffness versus space savings. Also, small form factor disc drives are typically so impacted for space due to slimness requirements that holes are now commonly punched out of the base plate into which stator winding coils are recessed to lower the stator height and allow more space inside the disc drive without increasing the size of the disc drive. However, forming a hole in a base plate and removing material from the base plate further lessens vibration resistance of an already thin base plate and thereby increases susceptibility to read-write errors of the disc caused by any vibration. Also, by removing material from the base plate, the base plate may become more susceptible to permanent deformation in the case of a shock event, in which, for example, the motor is jarred or dropped.
SUMMARYAn apparatus and method are described herein for stiffening a base plate of a spindle motor. A bearing is defined between a stationary component and a rotatable component, wherein the stationary component and the rotatable component are positioned for relative rotation. The stationary components include a base plate and a stator. The stator comprises at least one stator tooth. A stiffener tab, connected to, or integral with, the base plate, extends from the base plate, and is dimensioned to fit adjacent to at least one stator tooth, for stiffening the base plate. These and various other features and advantages will be apparent from a reading of the following detailed description.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Exemplary embodiments are described with reference to specific configurations. Those of ordinary skill in the art will appreciate that various changes and modifications can be made while remaining within the scope of the appended claims. Additionally, well-known elements, devices, components, methods, process steps and the like may not be set forth in detail in order to avoid obscuring the invention.
An apparatus and method are described herein for stiffening a base plate of a spindle motor to improve shock resistance and vibration response, and thereby increase reliability and performance of a disc drive memory system. Stiffening of a base plate is especially useful in the case of stamped base plate designs that typically have uniform thickness, whereas cast base plate designs are formed with thicker sections. When a base plate is cast, the present invention provides, in an embodiment, a stiffener tab formed along with the casting. In an embodiment, the present invention stiffens a motor cup portion of the base plate, thereby replacing stiffness lost by removal of material from the base plate used to form holes for recessing a stator.
Axial and angular displacement of a spindle motor during shock events and vibration are decreased. The improved axial and angular stiffness results in the read/write heads of a storage device being accurately aligned with storage tracks on a disc, when the device is subjected to vibration. This allows discs to be designed with increased track densities, and also allows for smaller discs and/or increased storage capacity of discs. Also, changes can be made to the natural frequency of the base plate axial and bending modes of vibration, therefore the present invention can further provide improved acoustic performance of the motor-base system.
It will be apparent that features of the discussion and claims may be utilized with disc drive memory systems, low profile disc drive memory systems, spindle motors, brushless DC motors, various fluid dynamic bearing designs including hydrodynamic and hydrostatic bearings, and other motors employing a stationary and a rotatable component, including motors employing conical bearings. Further, embodiments of the present invention may be employed with a fixed shaft or a rotating shaft. Also, as used herein, the terms “axially” or “axial direction” refers to a direction along a centerline axis length of the shaft (i.e., along axis 260 of shaft 202 shown in
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
A flex assembly provides the requisite electrical connection paths for the actuator assembly while allowing pivotal movement of the actuator body 126 during operation. The flex assembly (not shown) terminates at a flex bracket for communication to a printed circuit board mounted to the bottom side of disc drive 110 to which head wires are connected; the head wires being routed along the actuator arms 124 and the flexures 122 to the heads 120. The printed circuit board typically includes circuitry for controlling the write currents applied to the heads 120 during a write operation and a preamplifier for amplifying read signals generated by the heads 120 during a read operation.
Referring to
Since memory systems are being utilized in progressively more environments, a demand exists for smaller and thinner motors, and consequently thinner base plates.
The portion of the base plate that is displaced and defines the hole is utilized to form one stiffener tab, two stiffener tabs, or more than two stiffener tabs.
Additionally, in an embodiment, the present invention adjusts the natural frequency of the base plate axial and bending modes of vibration. The natural frequency is tuned by adjusting the number of stiffener tabs employed or by adjusting the size of the stiffener tabs such as length and height changes. Improved acoustic performance of the motor-base system can also be provided by the present invention. In cases where a base design has a natural frequency aligned with the electromagnetic frequencies of the motor, the natural frequencies of the base can be shifted using the stiffener tabs to reduce the base excitation and resulting acoustic emissions. Thus, the present invention is employed to adjust and benefit the system acoustic output as well. Additionally, the stiffener tabs can be used to improve effects from operating vibration response when the disc drive is subjected to external vibration from its environment. As an example, when a disc drive is vibrated at the same natural frequency as the motor base system, then the disc drive vibration response will considerably increase. In an embodiment, the present invention shifts the motor base resonance to a frequency that is out of range of any expected operating vibration, thus reducing the response to any operating vibration.
Referring to
Stiffener tab 334 can be formed to extend at angles other than a 90 degree angle with respect to a radially extending span 332 of the base plate 330. The selected angle for the stiffener tab 334 can be based on the available area for the stiffener tab 334, as well as the resulting stiffness and natural frequency of the base plate 330. The available area for the stiffener tab 334 is based on the clearance between the stator windings.
Turning now to
Stiffener tab 434 is formed from a portion of the base plate 430 that is displaced and defines a hole 435 within the base plate 430, and thus the stiffener tab 434 is situated adjacent to the hole 435. Here, the stiffener tabs 434 are dimensioned to fit adjacent to the stator teeth. When the stiffener tab is formed from a hole, the stiffener tab may be trimmed or otherwise shaped to fit adjacent to the stator teeth. When the stiffener tab is attached to a base plate, rather than being formed from a portion of a base plate that is displaced and defines a hole within the base plate, then the stiffener tab can be selectively shaped and placed.
As illustrated in
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While the embodiments described illustrate a stiffener tab extending from a base plate in a direction generally toward a stator, in an alternative embodiment, the stiffener tab extends from a base plate with a distal end oriented in a direction 180 degrees away from the stator.
Modifications and variations may be made to the disclosed embodiments while remaining within the spirit and scope of the invention. The implementations described above and other implementations are within the scope of the following claims.
Claims
1. A spindle motor system comprising:
- a bearing defined between a stationary component and a rotatable component, wherein the stationary component and the rotatable component are positioned for relative rotation, wherein the stationary component includes a base plate and a stator, and wherein the stator comprises at least one stator tooth; and
- a stiffener tab for stiffening the base plate, the stiffener tab extending from the base plate, and wherein: i.) at least a portion of the stiffener tab is dimensioned to fit and positioned circumferentially adjacent to the at least one stator tooth of the stator; and ii.) the stiffener tab extends along a radially extending span of the base plate.
2. (canceled)
3. The spindle motor system as in claim 1, wherein the stiffener tab is situated axially below the stator while being circumferentially adjacent to the stator.
4. The spindle motor system as in claim 1, wherein the stator comprises a first stator tooth and a second stator tooth, and wherein at least a portion of the stiffener tab is positioned circumferentially adjacent to the first stator tooth and the second stator tooth.
5. The spindle motor system as in claim 1, wherein the stiffener tab is formed from a portion of the base plate that is displaced and defines a hole within the base plate.
6. The spindle motor system as in claim 5, wherein the portion of the base plate that is displaced and defines the hole forms either one of the stiffener tab or two of the stiffener tab.
7. The spindle motor system as in claim 1, wherein the stiffener tab is formed from a material that is attached to the base plate.
8. The spindle motor system as in claim 1, wherein at least a portion of the stator is positioned within a hole defined within the base plate.
9. The spindle motor system as in claim 1, wherein the stiffener tab extends at a 90 degree angle with respect to a radially extending span of the base plate.
10. The spindle motor system as in claim 1, wherein the stiffener tab is further connected to a portion of the stator for further stiffening the base plate.
11. The spindle motor system as in claim 1, wherein the stiffener tab is formed with dimensions for filling an unoccupied area defined adjacent to the stator, wherein the dimensions of the stiffener tab are maximized to an extent without interfering with any motion of the spindle motor system.
12. The spindle motor system as in claim 1, wherein the base plate is created from one of a stamping process and a casting process.
13. The spindle motor system as in claim 12, wherein the stiffener tab is formed by casting when the base plate is cast.
14. The spindle motor system as in claim 1, wherein the stiffener tab is shaped to establish a predetermined natural frequency of the base plate axial and bending modes of vibration.
15. The spindle motor system as in claim 1, wherein the bearing is a fluid dynamic bearing.
16. In a spindle motor system including a bearing defined between a stationary component and a rotatable component, wherein the stationary component and the rotatable component are positioned for relative rotation, wherein the stationary component includes a base plate and a stator, and wherein the stator comprises at least one stator tooth, a method comprising:
- stiffening the base plate by employing a stiffener tab extending from the base plate, wherein: i.) at least a portion of the stiffener tab is dimensioned to fit and positioned circumferentially adjacent to the at least one stator tooth of the stator; and ii.) the stiffener tab extends along a radially extending span of the base plate.
17. (canceled)
18. The method as in claim 16, wherein the stiffener tab is situated axially below the stator while being circumferentially adjacent to the stator.
19. The method as in claim 16, wherein the stator comprises a first stator tooth and a second stator tooth, and wherein at least a portion of the stiffener tab is positioned circumferentially adjacent to the first stator tooth and the second stator tooth.
20. The method as in claim 16, wherein one of: the stiffener tab is formed from a portion of the base plate that is displaced and defines a hole within the base plate; and the stiffener tab is formed from a material that is attached to the base plate.
21. The method as in claim 16, wherein the stiffener tab is connected to a portion of the stator for further stiffening the base plate.
22. The method as in claim 16, wherein the stiffener tab is formed with dimensions for filling an unoccupied area defined adjacent to the stator, wherein the dimensions of the stiffener tab are maximized to an extent without interfering with any motion of the spindle motor system.
23. The method as in claim 16, wherein the stiffener tab is shaped to establish a predetermined natural frequency of the base plate axial and bending modes of vibration.
24. An apparatus comprising:
- a stator including at least one tooth; and
- a base plate including at least one associated stiffener tab that is configured to be circumferentially adjacent to the at least one tooth, wherein: i.) the stator is disposed adjacent to the base plate; and ii.) the stiffener tab extends along a radially extending span of the base plate.
Type: Application
Filed: May 3, 2008
Publication Date: Nov 5, 2009
Patent Grant number: 8476793
Inventor: Anthony J. Aiello (Santa Cruz, CA)
Application Number: 12/114,753
International Classification: H02K 5/24 (20060101); H02K 7/08 (20060101); H02K 15/14 (20060101);